A lithium secondary battery pack is made by combining a plurality of unit cells into one pack and is widely used in applications requiring high energy such as a vehicle battery or an electric power storage device.
However, a battery pack including a plurality of unit cells generates heat and swells up during overcharging, and thus is deformed such that a cell module expands outward.
In general, in order to cool the battery pack, a cooling passage through which a coolant is flown to achieve heat exchange is formed in a case of the battery pack. In this regard, Japanese Patent Publication No. 2001-297784 discloses a stacked solid state macromolecular fuel cell free from such a malfunction that a part of a cell constructing member like a separator or the like, contacting cooling water, is corroded during a continuous operation for a long period, that battery performance is lowered due to the increased conductivity of cooling water, or that safety during a leakage may not be ensured.
Also, Korean Patent Publication No. 2015-0111757 discloses a water cooling device for a water cooling battery module that is coupled to a water cooling unit sub-module, which receives battery cells therein and includes a coolant inlet pipe and a coolant outlet pipe provided on one side thereof, and is configured to circulate a coolant in the water cooling unit sub-module.
However, a conventional cooling passage has drawbacks in that the conventional cooling passage takes up a large space in a case, and when a coolant leaks, the coolant is flown in all directions in the case, thereby leading to a battery malfunction or a safety-related accident.